Closest supernova in 27 years may reveal fate of cosmos

An elderly star has lit up a cosmic cigar. Images of the galaxy M82, also known as the Cigar Galaxy, show the sudden appearance of a supernova, the brilliant explosion when a massive star dies. The event might offer new clues to dark energy and the ultimate fate of the universe.

The light from this explosion is reaching us from about 11.4 million light years away. That's not as close to Earth as the current record holder, which appeared about 160,000 light years away in a small satellite galaxy of the Milky Way. Still, that was in 1987 and the new supernova is the closest one we've spotted since then.

"It's very rare to have them go off as close as this one," says Brad Tucker at the Australian National University in Canberra. The supernova is not visible to the naked eye, but it is rapidly brightening and should be visible with binoculars in the next few weeks.

Ghostly arrivals

The relatively short distance to the supernova means it could provide a chance to detect one of the most fashionable objects in modern astronomy, the astrophysical neutrino. These ghostly particles rarely interact with ordinary matter, and were not spotted coming from outside the solar system until the 1987 supernova.

IceCube scientists say their observatory is unlikely to detect anything from M82 because the galaxy is too far away. But more sensitive detectors elsewhere may have already recorded them, as supernovas emit neutrinos before exploding with light. "They should be on some computer hard drive," says Tucker.

The explosion is also of a particularly useful variety known as type Ia. Astronomers use them as "standard candles" to measure distances in the universe, because all type Ias are thought to have the same brightness. This is important for understanding dark energy, the unknown force credited with the accelerating expansion of the universe.

Dark end

We think a type Ia supernova occurs when dense stellar corpses called white dwarfs interact with nearby stars, stealing matter until they reach a set mass and explode. But no one has seen this entire process happen.

That makes the new explosion especially exciting, as the Cigar Galaxy has been studied in detail thanks to images from the Hubble Space Telescope. "It is likely that the star that blew up has been directly imaged," says Tucker. "I'm actually working on that data right now."

If astronomers do find the dying star in past images and are able to make accurate readings of its brightness before and after the explosion, we might be able to reduce the uncertainties in our measurements of dark energy by a factor of two, says Tucker. That would be enough to distinguish between different models of dark energy and its ultimate impact on the fate of the universe.

"One single star that blew up could help us figure out how the universe will end," says Tucker.

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The M82 galaxy is the proud owner of this type Ia supernova, and right now all eyes are on it (Image: UCL/University of London Observatory/Steve Fossey/Ben Cooke/Guy Pollack/Matthew Wilde/Thomas Wright)